OBJECTIVETo observe the best dose of methylprednisolone improving lung injury in swine with paraquat intoxication.

METHODSAcute lung injury (ALI/ARDS) model was made by an intraperitoneal injection of a large dose of 20%PQ solution20 millilitres in swine. Then 24 swine were randomly divided into 4 groups: exposed PQ control group, 5 mg/kg of methylprednisolone group, 15 mg/kg of methylprednisolone group, 30 mg/kg of methylprednisolone group. All groups were based on the conventional rehydration for intervention, Arterial blood samples were collected before modeling and 0, 12, 24, 36 hours after different processing for blood gas analysis. At the same time heart rate (HR), mean arterial pressure (MAP), extravascular lung water index (EVLWI) and pulmonary vascular permeability index (PVPI) were measured by using PICCO (pulse indicator continuous cardiac output), lung tissue was obtained by punctureneedle to produce lung biopsy, then observe the pathological changes of lung tissue in the microscope.

RESULTS1. Comparison between groups: there is no significant difference about extravascular lung water index (EVLWI) and semi-quantitative score of lung tissue pathology in four groups (P > 0.05) before modeling, so is t0, there is significant difference at about extravascular lung water index and semi-quantitative score of lung tissue pathology 12 h, 24 h and 36 h after different processing (P < 0.05). Within the group: EVLWI and semi-quantitative score of Lung tissue pathology in four groups significantly increased when the model was made (P < 0.05), after different processing, EVLWI and semi-quantitative score of Lung tissue pathology in exposed PQ control group kept going up, in other three groups, EVLWI and semi-quantitative score of lung tissue pathology went down first and then went up, there is significant difference compared with t0 (P < 0.05). 2. Comparison between groups: there is no significant difference about oxygenation index in four groups (P > 0.05) before modeling, so is t0, there is significant difference about oxygenation at 12 h, 24 h and 36 h after different processing (P < 0.05). Within the group: oxygenation index in four groups significantly decreased when the model was made (P < 0.05), after different processing, oxygenation index in exposed PQ control group kept going down, in other three groups, it showed a downward trend after the first rise, there is significant difference compared with t0 (P < 0.05). 3. After medication for 36h, correlation analysis showed that EVLWI were negatively associated with oxygenation index (r = -0.427, P = 0.022) and positively associated with semi-quantitative score of Lung tissue pathology (r = 0.903, P = 0.034).

CONCLUSIONMethylprednisolone can obviously relieve lung injury caused by paraquat poisoning and improve oxygenation. After the model was made, within 24 hours, 30 mg/kg of methylprednisolone have advantage for the PQ poisoning swine, but 15mg/kg of methylprednisolone is best for improving lung injury induced by paraquat intoxication within 24 hours to 36 hours.